Stem Cells' Dirty Little Secret

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Stem Cells' Dirty Little Secret

Pssst... I recently learned a dirty little secret about "adult stem cells" that I'd like to let you in on.

Adult stem cells are the kind touted by social conservatives when they're explaining why embryonic stem cell research is unnecessary. They say studying adult stem cells, the type that aren't derived by killing an embryo, already work as just as well as therapies if not better, without the nasty side effects.

But guess what? Adult stem cells kill. They're mass murderers, in fact. In only four years from 2000 through 2004, adult stem cells have been complicit in at least 3,629 American deaths – 624 of which involved children under the age of 18. If the trend continues adult stem cells will claim their 5,000th victim since 2000 this year.

Sites like the Family Research Council, Center for Bioethics and Human Dignity (CBHD), World Net Daily, and Do No Harm all recite the same argument: therapies derived from embryonic stem cells will form tumors, therefore the risks are too great to justify spending the public's money to study them. Instead, they say, adult stem cells – taken from bone marrow, blood, hair follicles and various other locations without harming the human body – are a better use of taxpayer money.

The terrible irony is that unlike embryonic stem cells, adult stem cells are already proven to be dangerous and sometimes deadly to humans in the form of graft-versus-host disease (GVHD).

Two of those sites – CBHD and Do No Harm mention GVHD only as a problem embryonic stem cells will face. David Prentice, a co-founder of Do No Harm, puts it this way: "embryonic cells already have the molecules on their surface which [can] lead to ... a response of the transplant against the host (graft-versus-host disease.)" That scientists won't be able to get around this problem is speculation, since embryonic stem cells have not yet led to human therpies. But adult stem cells have already proven their ability to induce GVHD. Prentice conveniently does mention it.

As Prentice accurately describes, GVHD is a condition in which a transplant – such as bone marrow – attacks the recipient, or host. GVHD can be either acute, beginning within the first 100 days post-transplant, or chronic, beginning anytime thereafter.

Complications of acute GVHD (.pdf) arise from attacks against the skin, liver, and intestines. They range from the mild: skin rash, nausea, and cramping, to severe: blisters, bloody diarrhea, and death. Chronic GVHD (.pdf) complications include attacks on the aforementioned organs, as well as any other organs.

It's incredible to imagine they don't know about the risks associated with adult stem cell therapies. The risks of GVHD after bone marrow transplants are well-documented by the National Cancer Institute. Prentice fancies himself an expert on the magical powers of adult stem cells, and Weldon is an M.D. Early reports of GVHD, then known as "runt disease," were enough of a concern to merit mention in a 1960 Nobel Lecture, so the risks have been known for more than 40 years.

Maybe not mentioning the risks of adult stem cells is an honest mistake by adult stem cell boosters. A less charitable explanation is that ESC opponents knowingly mislead the public about the safety of adult stem cells, glossing over GVHD deaths in their desire to discredit embryonic stem cell research.

Granted, the risk of GVHD is one a leukemia patient is usually willing to take. Similarly, people like me who are waiting for cures might be willing to take certain risks associated with embryonic stem cell therapies.

In the meantime, let's at least have an honest debate. And let's give scientists ample funding to solve potential complications – like GVHD – and let science lead the way.